The aim of the study was to evaluate the effectiveness of two different sedation protocols for a brief
standing procedure in horses.
Fourteen standardbreed horses undergoing gastroscopy for diagnostic purposes were involved in the study.
Approval for ethical committee of University of Pisa was obtained. Animals were divided in two groups:
group XX, that received a sedation with a bolus of xylazine 0.75 mg/kg IV followed by a xylazine variable
rate infusion and group XD, that received a sedation with a bolus of xylazine 0.75 mg/kg IV followed by a
dexmedetomidine variable rate infusion. The infusion rate was modified by an operator based on the
evaluation of the sedation state.
Sedation was assessed with a multiparametric index of sedation by considering posture, response to a vocal
stimulus, position of head and neck, position of the lower lip and tongue and position of the eyelid. During
the procedure heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP) end tidal CO2 (EtCO2)
were recorded before the administration of sedation (Tbase) and every five minutes for 25 minutes.
No differences were detected between Tbase and the subsequent time points for HR, RR and EtCO2 in both
groups. Concerning MAP in the XX group a significant difference of Tbase values was found in comparison
to T5, T10, T15 and T20 time points. No differences were found for XD group for MAP. Sedation score in XD
was significantly higher at T10, T15 and T20 compare with Tbase, while in XX group Tbase values were
significantly lower than T10, T15, T20 and T25. Median infusion dosage of dexmedetomidine was 5
mcg/kg/h (range 2-9) while median xylazine infusion dosage was 0.4 mg/kg/h (range 0.26-0.69). Mean time
from infusion stop and coordinate movement of the horses was 12.5 ± 5 minutes for XX group and 6.8 ± 2
minutes for XD group.
Both sedation protocols resulted appropriate for the procedure. The infusion rate was modified in order to
adequate the sedation plane to the stimuli in both groups. In the XD group a lower hypertensive effect was
registered in comparison to XX group. The sedation plane in XX group was more stable but horses required
a longer time to move out from the stock